This invention relates to rearview mirrors for motor vehicles and, more particularly, to improved electrochromic rearview mirror assemblies and subassemblies.
Existing interior and exterior rearview mirror assemblies may both incorporate one or more electronic accessories that utilize a circuit board to support and interconnect the circuit components of the one or more electronic accessories. Placement of the circuit board on the rear of the mirror element or within the housing of the mirror assembly can present certain problems. Specifically, placement of a circuit board within a rearview mirror assembly increases the complexity, component count and cost of the mirror assembly. In addition, it imposes styling constraints due to the need to make the housing larger and deeper to accommodate and support the circuit board. Further, circuit boards require many interconnections to the various electronic components within the assembly. For example, when mounting a display behind the mirror element, a separate daughter circuit board is often required for the display since the display is mounted facing the mirror element while the other components are typically mounted facing the opposite direction on the mother circuit board. Thus, interconnections are required between the mother and daughter boards and the use of two boards increases the volume occupied by the circuit boards within the housing. Similarly, light sensors, pushbuttons and indicator lights are typically mounted so as to face rearward relative to the vehicle sometimes requiring special mounting relative to other components on the circuit board or may require a separate circuit board facing the opposite direction. Likewise, interconnections may be required to microphones mounted on the top or bottom surface of the mirror housing. If the mirror element is an electrochromic mirror element or some other electro-optic variable reflectance mirror element, interconnections to the electrodes of the electro-optic mirror element are also required. Map lights may also require a separate interconnected circuit board. In outside mirrors, interconnections may be required to LEDs or other lights functioning as a turn signal or as an exterior illuminator. All of these interconnections add to the complexity, cost and component count of the mirror assembly.
Because of the need for all of the above-noted interconnections to other components within the mirror housing, it may not be possible to test the circuit boards and the interconnected components until after final assembly. This may result in more of the assembly being scrapped in the event of component failure.
Providing circuit components on circuit boards can result in the inadvertent generation of electromagnetic fields at levels that cause interference to other electronic components within the vehicle, such as the vehicle radio. In addition, circuit components provided on circuit boards may be subject to electromagnetic interference (EMI) from other vehicle accessories thereby resulting in improper operation. In some situations, it may become necessary to utilize additional components or techniques to reduce the EMI levels generated by the circuit components on the circuit board or to improve the immunity of the circuit components to EMI generated by other vehicle accessories.